Phenylalanine-glycine derivatives, process for preparation thereof, and pharmaceutical composition containing said derivatives

A process for preparing an L-phenylalanine-glycine derivative of the general formula (I):

• ##STR20## wherein R represents a residue of an antitumor substance, or a salt or an ester thereof, comprising the steps of:
• (1) reacting carbobenzoxychloride with a salt of phenylalanineamide of the formula (V):
• ##STR21## to obtain a compound of the formula (IV):
• ##STR22## (2) reacting the resulting compound of the formula (IV) with a glyoxylic acid compound of the general formula (VI):
• ##STR23## wherein R.sup.2 represents a benzyloxy group or an alkoxy group with 1 to 4 carbon atoms, to obtain a compound of the general formula (IIIa):
• ##STR24## wherein R.sup.2 has the same meaning as above, (3) reacting the resulting compound of general formula (IIIa) with acetic anhydride to obtain a compound of the general formula (IIIb):
• ##STR25## wherein R.sup.2 has the same meaning as above, (4) reacting the resulting compound of the general formula (IIIb) with the antitumor substance to obtain a compound of the general formula (II):
• ##STR26## wherein R and R.sup.2 have the same meanings as above, and (5) removing the protecting group(s) from the resulting compound of the general formula (II).